1. Field of the Invention
The present invention relates to a magnetic master transfer medium provided with an uneven pattern for transferring data to a slave medium, and the usage method thereof.
2. Description of the Related Art
Generally speaking, with regard to magnetic storage mediums, those having a high storage capacity to record an increasing amount of data are desired. More preferably, so-called high-speed access mediums capable of advantageously reading out the data of a desired location in a short time are desired. One example of these mediums is the high density magnetic disk medium employed in hard disk or flexible disk apparatuses; so-called tracking servo technology, wherein the magnetic head accurately scans a narrow width track to achieve a high S/N ratio, plays a substantial role in realizing the high storage capacity thereof. A servo signal, address data signal, replay clock signal, etc., used for tracking within a certain interval occurring in one rotation of the disk are recorded in advance in a so-called preformatting, and the magnetic head is set so as to be capable of reading out the preformatted signals and correcting its position thereby, whereby the magnetic head can accurately scan the track.
In general, the servo signal (the servo pattern) is formed in the following order from the starting position of the servo frame: a preamble (a concurrent use signal), a gray code (the track number signal), and a burst signal (the signal determining the head position), and a data region follows thereafter. A portion of the burst signal is recorded at a distance displaced by xc2xd the width of the track from the center line of said track, and the remaining components of the servo signal are recorded on the center line of the track at an entire track pitch width. Further, the data region is narrower than the recording width of the servo signal, and a guard band portion is formed at the portions adjoining the inner and outer tracks thereto, which prevents the recording of a signal thereon.
At present, a preformat such as that described above employs a specialized servo recording apparatus, and is formed by writing the signal for one disk at a time, on one track at a time. The servo recording apparatus is provided with a magnetic head, which has a head width of, for example, 75% of the track pitch, and first rotates the disk one rotation with the magnetic head disposed adjacent to the disk; the pattern corresponding to the outer xc2xd track is written, after which the magnetic head is moved xc2xd track pitch inward and the pattern corresponding to the inner xc2xd track is written during the next rotation of the disc, whereby a one track portion of signal is written.
The servo recording apparatus described above is of high cost, and because a significant amount of time is required for the preformatting operation, this process accounts for the larger part of the manufacturing costs; reducing these costs is desirable.
In this regard, methods wherein the preformat data is transferred by a magnetic transfer, which is a method by which preformat data is not written one track at a time, has been proposed: for example, magnetic transfer technologies are introduced in Japanese Unexamined Patent Publication Nos. 10(1998)-269566, 10(1998)-40544, etc. According to the magnetic transfer of these methods: a master medium having an uneven pattern corresponding to the data to be transferred to the slave medium, which is a magnetic transfer medium such as a magnetic disk or the like, is prepared; this master medium is brought into a state of close contact with the slave medium; then, by applying a transfer magnetic field, the magnetic pattern corresponding to the data carried by the uneven pattern (e.g., a servo signal) of the master medium is transferred to the slave medium; the preformatting can be performed without changing the relative positions of the master medium and the slave medium, that is, while the two media remain stationary; and not only is it possible to perform an accurate recording of the preformat data, it becomes possible to do so in an extremely short time.
In order to improve the transfer quality of a magnetic transfer such as that described above, it is important that the master medium and the slave medium be disposed in close contact with each other in a manner wherein there is no gap therebetween. That is to say, if the two media are not properly brought into close contact with each other, regions in which the magnetic transfer is not effected occur, and signal omissions occur in the magnetic data transferred to a slave medium onto which the transfer has not been properly effected, producing a decrease in the signal quality thereof; for cases in which the recorded signal is a servo signal, a problem arises in that the tracking function is insufficient, resulting in a decrease in reliability.
To solve this problem, technologies have been proposed, in, see for example, Japanese Unexamined Patent Publication No. 11(1999)-161956, wherein the center portion of the master medium is formed as a curved protrusion, with respect to the slave medium, and when the master and slave mediums are brought into contact, the surface of the master medium deforms to become progressively flatter from the center portions thereof toward the periphery due to the pressure exerted thereon, and they are brought into close contact in a manner so that no air remains between two surfaces thereof, whereby the contact characteristics therebetween are improved.
However, in order to facilitate the transferal to the slave medium the same signal pattern servo written to the slave medium when the servo recording apparatus described above is employed, the uneven pattern formed on the master medium is formed by protrusions and depressions of a width equivalent to the track pitch (the track width) of the slave medium. More specifically, as shown in the partial perspective view of the form of the uneven pattern formed on the surface of the master medium illustrated in FIG. 13, the protrusion portion 71, which has a width in the direction of the track pitch (direction Y) equivalent to the width of the track pitch P, is formed within one track or straddling two tracks.
Because these types of protrusion portions 71 are formed contiguously in the in the direction of the track (direction X) and in the direction of the track pitch (direction Y), as shown by the diagonal lines within FIG. 13, there are cases in which a depression portion 72 is formed surrounded on all four sides by protrusion portions 71. If there are depression portions 72 of this type, that is, which are surrounded on four sides by protrusion portions 71, even if a technology of the type proposed in the aforementioned Japanese Unexamined Patent Publication No. 11(1999)-161956 for improving the contact characteristics between the surface of the master medium and the surface of the slave medium is employed, in actuality, when the master medium and the slave medium are brought into close contact, the protrusion portions 71 surrounding the depression portion 72 end up being brought into close contact with the slave medium first and the air held in the thus closed off depression portion 72 is not removed, whereby a problem arises in that adequate contact characteristics cannot be obtained as a result of this air remaining within the space of the closed off depression portion 72.
Further, because the magnetic transfer is performed in the state wherein the master and slave mediums have been brought into close contact as described above, cases occur in which the position determining of the master medium and the slave medium is performed while they are in the close contact state before the magnetic transfer is performed, and due to the friction generated by the rubbing together of the respective contact surfaces of the master medium and the slave medium during this position determining, the surface form of the pattern bearing the data of the master medium is worn away after repeated performance of the magnetic transfer, whereby the accuracy of the transfer is deteriorated. It is necessary to replace the master medium if the surface form of the pattern bearing the data thereof is worn away and the accuracy of the magnetic transfer thereby reduced; because the cost of the master medium is extremely high, the problem regarding how many slave mediums a single master medium can be used to transfer to is extraordinarily important in relation to controlling manufacturing costs.
Meanwhile, if there is even one portion between the master medium and the slave medium that has poor contact when said two mediums are brought into close contact, the positional relation between both of said mediums cannot be maintained across the entirety of the respective surfaces thereof, and the transfer quality is reduced. Also, according to the specific circumstances, there are cases in which regions to which the transfer has not been effected appear due to poor contact between the two mediums, and signal omissions occur in the magnetic data transferred to a slave medium onto which the transfer has not been properly effected, producing a decrease in the signal quality; for cases in which the recorded signal is a servo signal, a problem arises in that the tracking function is insufficient, resulting in a decrease in reliability.
The present invention has been developed in view of the foregoing circumstances, and it is a primary object of the present invention to provide a master medium capable of effecting a high quality magnetic transfer to a slave medium, wherein no signal omissions occur in the magnetic data transferred thereto.
It is a further object of the present invention to provide a long-life magnetic transfer master medium capable of transferring magnetic data to a larger number of slave mediums.
The magnetic transfer master medium according to the present invention is a magnetic transfer master medium that is provided with an uneven surface for transferring data to a slave medium, wherein
the uneven pattern is formed so that there are no depression portions therein that are completely surrounded by protrusion portions.
The phrase xe2x80x9cformed so that there are no depression portions therein that are completely surrounded by protrusion portionsxe2x80x9d means that the uneven pattern is formed so that there is at least one portion on the immediate periphery of each depression portion, through which air can be expelled when the master and the slave medium are brought into close contact; for example, the width of the protrusion portions in the direction of the track pitch of the uneven pattern can be formed so as to be narrower than said track pitch.
Note that it is not necessary that the width of all of the protrusions portions be formed so as to be narrower than said track pitch; it is permissible that only a portion of the protrusion portions be formed so that the width thereof in the direction of the track pitch is narrower than said track pitch. In this case, the uneven pattern can be of a configuration wherein, for example, the protrusion portions formed within a single track can be formed so that the width thereof in the direction of the track pitch is narrower than said track pitch; also, the protrusion portions formed so as to straddle adjacent tracks can be formed so that the width thereof in the direction of the track pitch is substantially equal to said track pitch.
Another magnetic transfer master medium according to the present invention is a magnetic transfer master medium that is provided with an uneven surface for transferring data to a slave medium, wherein
a rough surface is formed on the surface of the protrusion portions of the uneven pattern.
Note that the rough surface formed on the surface of the protrusion portions of the uneven pattern can be formed on a portion or the entirety thereof. Further, the rough surface is not limited to being capable of being formed on the protrusion portions; no problem is incurred if the rough surface is formed on the surface of the depression portions as well.
More specifically, the magnetic transfer master medium described above comprises, for example, a substrate, and an uneven pattern provided thereon, which is provided with a pliable magnetic layer formed on at least the sections constituting the protrusion portions thereof; wherein, the rough surface corresponds to a rough surface formed, by use of a surfacing process, on at least the sections of the substrate on which the pliable magnetic layer has been provided. Here, as to the surfacing process to which the substrate is subjected, a process such as a texturing process performed by grinding or a texturing process performed by use of a laser can be employed, or alternatively, a process that causes erosion on the surface, may be employed.
Further, the magnetic transfer master medium according to the present invention may comprise a substrate, a granular material coated onto the sections of the uneven pattern formed on said substrate that constitute at least the protrusion portions thereof, and a pliable magnetic layer formed on said granular substance; wherein, the rough surface is formed according to the surface form of the protrusion portions coated with the granular material.
Still further, the aforementioned other magnetic transfer master medium according to the present invention comprises a substrate, and an uneven pattern formed thereon, which is provided with a pliable magnetic layer formed on at least the sections constituting the protrusion portions thereof; wherein, the rough surface can be formed according to the formation conditions of the pliable magnetic layer, that is, can be formed as a surface roughness controlled by the sputtering conditions or the like, for example.
In addition, yet another magnetic transfer master medium according to the present invention comprises a substrate, an uneven pattern formed thereon, which is provided with a film of porous material on at least the sections constituting the protrusion portions thereof, and a pliable magnetic layer formed on the film of porous material; wherein, the rough surface can be formed according to the surface form of the film of porous material. In this case, it is desirable that the film of porous material have a volume ratio in the range of 30-99%, and a surface roughness in the range of Rp=0.0001 to 0.1.
Note that according to the magnetic transfer master medium described above, it is desirable that the rough surface is an uneven surface having depression portions of a depth in the 3-50 nm range; and it is more preferable that said depth be in the 5-20 nm range.
Yet another magnetic transfer master medium according to the present invention is a magnetic transfer master medium provided with an uneven surface for transferring data to a slave medium; wherein, the channels of the uneven pattern are of a depth in the 50-1000 nm range immediately after the manufacture of said medium, and the surface of the protrusion portions is ground at least once after the manufacture and before the use of said medium, and then the medium is used.
Further, yet still another magnetic transfer master medium according to the present invention is a magnetic transfer master medium provided with an uneven surface for transferring data to a slave medium; wherein, the channels of the uneven pattern are of a depth in the 50-1000 nm range immediately after the manufacture of said medium, and the surface of the protrusion portions is ground at least once after said medium has been used, and then said medium is reused.
The phrase xe2x80x9cimmediately after the manufacturexe2x80x9d refers to the master medium in the state occurring after a series of manufacturing processes has been completed and the medium is capable of being used for performing magnetic transfer, and the medium has not yet been used. Accordingly, in general, during the course of carrying out manufacturing processes to make a magnetic transfer master medium, a grinding process, for example, is performed for cases such as those in which burrs are present on the surface of the protrusion portions of the uneven pattern, or the like; this grinding process differs from the grinding process described above.
Further, the referents of xe2x80x9cafter the manufacture and before the use of said mediumxe2x80x9d can include the state immediately after the manufacture of the medium has been completed and before it has been used, and the state occurring after the medium has been used once and before the medium has been reused.
The method of using the magnetic transfer master medium according to the present invention is a method of using a magnetic transfer master medium provided with an uneven surface for transferring data to a slave medium; wherein, said magnetic transfer master medium is used after the surface of the protrusion portions of the uneven pattern has been ground at least once immediately after the manufacture of said medium.
Further, another method of using the magnetic transfer master medium according to the present invention is a method of using a magnetic transfer master medium provided with an uneven surface for transferring data to a slave medium; wherein, said magnetic transfer master medium is reused after the surface of the protrusion portions of the uneven pattern has been ground at least once after said master medium has been used.
Still further, each of the above-described methods of using the magnetic transfer master medium according to the present invention can be a method wherein the surface of the protrusion portions of the uneven pattern formed on the magnetic transfer master medium is ground according to the extent to which said surface is marred.
Here, the phrase xe2x80x9cground according to the extent to which said surface is marredxe2x80x9d can refer to the performance of the grinding of the surface of the protrusion portions of the uneven pattern based on a predetermined number of times or a predetermined number of days which the medium has been used, or based on an inspection of the surface form of the surface of said protrusion portions.
According to the magnetic transfer master medium of the present invention, because the uneven pattern has been formed so that there are no depression portions that are surrounded by protrusion portions on all four sides, the problem occurring when a conventional magnetic transfer master medium is used, as described above, wherein air remains in the depression portions surrounded on all four sides by protrusion portions when the master and slave mediums are brought into close contact and the contact property between the respective surfaces has been thereby deteriorated, can be avoided, and the contact property between the master and slave mediums can be improved. By improving the contact property between the master and slave mediums, signal omissions can be prevented, and the quality of the transferred signal can be improved.
According to another magnetic transfer master medium of to the present invention, because a rough surface has been formed on the surface of the protrusion portions of the uneven pattern, which is brought into contact with the slave medium, compared to the case in which the surface of the protrusion portions of a conventional magnetic transfer master medium is brought into contact with a slave medium, because the actual surface area with which the surface of the slave medium is brought into contact can be made smaller, the coefficient of the friction, in particular, that occurring between said two surfaces during the performance of the position determining thereof when both of said surfaces are brought into close contact can be lowered; as a result, the wear-out period of the uneven pattern can be extended. Accordingly, the life span of the master medium can be lengthened, whereby it becomes possible to transfer data to a larger number of slave mediums. Therefore, the costs incurred in performing magnetic transfer can be reduced, and preformatted slave mediums can be provided at a low cost.
Further, after the slave medium has been brought into close contact with the master medium and the transfer has been effected, there are cases in which it is difficult to peel the slave medium from the master medium, and it becomes necessary to apply an excessive amount of force to effect the separation thereof; although this excessive force is sometimes the cause of damage to the mediums, according to the present invention, if the actual contact surface area between said two mediums is small, an effect is produced whereby one potential cause of damage to said mediums is eliminated.
Still further, by forming a rough surface, because it becomes easy to remove air when the slave medium is brought into close contact with the master medium, the contact characteristics between the respective surfaces of the master and the slave medium can be improved. By improving these contact characteristics, the occurrence of signal omissions can be prevented, and the recording quality of the transferred signal can be improved.
According to yet another magnetic transfer master medium of the present invention, because the surface of the protrusion portions of the uneven pattern formed on said medium magnetic transfer master medium is ground at least once after the manufacture thereof and before said medium is used, even if the surface of said protrusion portions is marred, the marks thereon can be removed by the grinding process and the medium can be provided for use having a desirable surface state.
According to still yet another magnetic transfer master medium of the present invention, because the surface of the protrusion portions of the uneven pattern formed thereon is ground at least once after said medium has been used, and then said medium is reused, even if the surface form of said protrusion portions is worn due to usage, or has been marred by dust or other foreign matter that has adhered thereto, the surface state can be restored by the grinding process and the medium can be made available for reuse having a desirable surface state.
According to the method of using the magnetic transfer master medium according to the present invention, because the magnetic transfer master medium is used after the surface of the protrusion portions of the uneven pattern formed thereon has been ground at least once immediately after the manufacture of said medium, even for cases in which the surface of said protrusion portions is marred, said medium is used after said marks have been removed by the grinding process, whereby it becomes possible to obtain a high quality magnetic transfer. Further, in this way, the master medium can be used repeatedly; as a result, the life span of the master medium can be lengthened, whereby it becomes possible to transfer magnetic data therefrom to a larger number of slave mediums. Accordingly, the cost incurred in the magnetic transfer operation can be cut, whereby it becomes possible to provide preformatted slave mediums at a lower price.
Further, according to another method of using the magnetic transfer master medium according to the present invention, because said magnetic transfer master medium is reused after the surface of the protrusion portions of the uneven pattern has been ground at least once after said medium has been used, even for cases in which the surface state of said protrusion portions is worn out due to usage, and including cases in which said surface state has been marred by dust or other foreign matter that has adhered thereto, said medium is used after said marks have been removed and the surface state thereof has been restored by the grinding process, whereby it becomes possible to obtain a high quality magnetic transfer. Further, in this way, the master medium can thereby be used repeatedly; whereby the life span of the master medium can be lengthened, and the and it becomes possible to transfer magnetic data therefrom to a larger number of slave mediums. Accordingly, the cost incurred in the magnetic transfer operation can be cut, whereby it becomes possible to provide preformatted slave mediums at a lower price.